The present invention relates to cigarette-type smoking articles that produce an aerosol resembling tobacco smoke, but which contain no more than a minimal amount of incomplete combustion or pyrolysis products.
Many smoking articles have been proposed through the years, especially over the last 20 to 30 years.
Tobacco substitutes have been made from a wide variety of treated and untreated plant material, such as cornstalks, eucalyptus leaves, lettuce leaves, corn leaves, cornsilk, alfalfa, and the like. Numerous patents teach proposed tobacco substitutes made by modifying cellulosic materials, such as by oxidation, by heat treatment, or by the addition of materials to modify the properties of cellulose. One of the most complete lists of these substitutes is found in U.S. Pat. No. 4,079,742 none of the extensive efforts, it is believed that proposed products has been found to be satisfactory as a tobacco substitute.
Many smoking articles have been based on the generation of an aerosol or a vapor. Some of these products purportedly produce an aerosol or a vapor without heat. See, for example, U.S. Pat. No. 4,284,089 to Ray. However, the aerosols or vapors from these articles fail to adequately simulate tobacco smoke.
Some proposed aerosol generating smoking articles are believed to have used a heat or fuel source in order to produce an aerosol. One of the earliest of these proposed articles is described by Siegel in U.S. Pat. No. 2,907,686. The Siegel reference proposed a cigarette substitute which includes an absorbent carbon fuel, preferably a 2.5 inch (63.5 mm) stick of charcoal, which is burnable to produce hot gases, and a flavoring agent carried by the fuel, which is adapted to be distilled off incident to the production of the hot gases. Siegel also proposed that a separate carrier, such as clay, may be used for the flavoring agent, and that a smoke-forming agent, such as glycerol, may be admixed with the flavoring agent. Siegel's proposed cigarette substitute may be coated with a concentrated sugar solution to provide an impervious coat and to force the hot gases and flavoring agents to flow toward the mouth of the user. It is believed that the presence of the flavoring and/or smoke-forming agents in the fuel of Siegel's article would cause substantial thermal degradation of those agents and an attendant off-taste. Moreover, it is believed that the article would tend to produce substantial sidestream smoke containing the aforementioned unpleasant thermal degradation products.
Another smoking article is described by Ellis et al in U.S. Pat. No. 3,258,015. Ellis et al proposed a smoking article which has an outer cylinder of fuel having good smoldering characteristics, preferably fine cut tobacco or reconstituted tobacco, surrounding a metal tube containing tobacco, reconstituted tobacco, or other source of nicotine and water vapor. It is believed that upon smoking, the burning fuel heats the nicotine source material to cause the release of nicotine vapor and potentially aerosol generating material, including water vapor. It is proposed that the vaporized materials are mixed with heated air which enters the open end of the tube. A substantial disadvantage of this article includes the ultimate protrusion of the metal tube as the tobacco fuel is consumed. Other apparent disadvantages of this proposed smoking article included the presence of substantial tobacco pyrolysis products, the substantial tobacco sidestream smoke and ash, and the possible pyrolysis of the nicotine source material in the metal tube.
In U.S. Pat. No. 3,356,094, Ellis et al disclose a modification of their original design to eliminate the protruding metal tube upon use. The allegedly improved design employed a tube made out of a material, such as certain inorganic salts or an epoxy bonded ceramic, which is disclosed as becoming frangible upon heating. This frangible tube is disclosed as being removable when the smoker eliminates ash from the end of the article. Even though the appearance of this article is very similar to a conventional cigarette, apparently no commercial product ever has been marketed.
In U.S. Pat. No. 3,738,374, Bennett proposed the use of carbon or graphite fibers, mat, or cloth associated with an oxidizing agent as a substitute cigarette filler. Flavor is provided by the incorporation of a flavor or fragrance into the mouthend of an optional filter tip.
U.S. Pat. Nos. 3,943,941 and 4,044,777 to Boyd et al and British patent No. 1,431,045 proposed the use of a fibrous carbon fuel which is mixed or impregnated with volatile solids or liquids which are capable of distilling or subliming into the smoke stream to provide "smoke" to be inhaled upon burning of the fuel. Among the enumerated smoke producing agents are polyhydric alcohols, such as propylene glycol, glycerol, and 1,3-butylene glycol, and glyceryl esters, such as triacetin. Despite Boyd et al's desire that the volatile materials distill without chemical change, it is believed that the mixture of these materials with the fuel would lead to substantial thermal decomposition of the volatile materials and to bitter off tastes. Similar products are proposed in U.S. Pat. No. 4,286,604 to Ehretsmann et al and in U.S. Pat. No. 4,326,544 to Hardwick et al.
Bolt et al, in U.S. Pat. No. 4,340,072, proposed a smoking article having a fuel rod with a central air passageway and a mouthend chamber containing an aerosol forming agent. The fuel rod preferably is a molding or extrusion of reconstituted tobacco and/or tobacco substitute, although the patent also proposed the use of tobacco, a mixture of tobacco substitute material and carbon, or a sodium carboxymethylcellulose (SCMC) and carbon mixture. The aerosol forming agent is proposed to be a nicotine source material, or granules or microcapsules of a flavorant in triacetin or benzyl benzoate. Upon burning during use of the article, air enters the air passage where it is mixed with combustion gases from the burning rod. The flow of these hot gases reportedly ruptures the granules or microcapsules to release the volatile material. This material reportedly forms an aerosol and/or is transferred into the mainstream aerosol. It is believed that the articles of Bolt et al, due in part to the long fuel rod, would produce insufficient aerosol from the aerosol former to be acceptable, especially in the early puffs. The use of microcapsules or granules further would appear to impair aerosol delivery because of the heat needed to rupture the wall material. However, total aerosol delivery would appear dependent on the use of a large mass of tobacco or tobacco substitute materials, which would provide substantial pyrolysis products and sidestream smoke. Such attributes would not be desirable in such types of smoking articles.
U.S. Pat. No. 3,516,417 to Moses proposed a smoking article, with a tobacco fuel, which is essentially identical to the article of Bolt et al, tobacco in lieu of the granular or microencapsulated flavorant of Bolt et al. (See FIG. 4, and col. 4 lines 17-35 of the Moses reference.) Similar tobacco-based fuel articles are described in U.S. Pat. No. 4,347,855 to Lanzilotti et al and in U.S. Pat. No. 4,391,285 to Burnett et al. European patent application No. 117,355, by Hearn et al, described similar smoking articles having a pyrolyzed ligno-cellulosic heat source with an axial passageway therein. These articles would be expected to suffer many of the same problems as the articles proposed by Bolt et al.
Steiner, in U.S. Pat. No. 4,474,191, described "smoking devices" containing an air-intake channel which, except during the lighting of the device, is completely isolated from the combustion chamber by a fire resistant wall. To assist in the lighting of the device, Steiner proposed providing a means for allowing the brief, temporary passage of air between the combustion chamber and the air-intake channel. Steiner's heat conductive wall also serves as a deposition area for nicotine and other volatile or sublimable tobacco simulating substances. In one embodiment (FIGS. 9 and 10), the Steiner device is provided with a hard, heat transmitting envelope. Materials reported to be useful for the envelope include ceramics, graphite, metals, etc. In another embodiment, Steiner envisions the replacement of the tobacco (or other combustible material) fuel source with some purified cellulose-based product in an open cell configuration, mixed with activated charcoal. This material, when impregnated with an aromatic substance, is stated to dispense a smoke-free, tobacco-like aroma.
None of the foregoing types of smoking articles have ever achieved any commercial success, and it is believed that none has ever been widely marketed. The absence of such smoking articles from the marketplace is believed to be due to a variety of reasons, including insufficient aerosol generation, both initially and over the life of the product, poor taste, off-taste due to the thermal degradation of the smoke former and/or flavor agents, the presence of substantial pyrolysis products and sidestream smoke, and unsightly appearance.
More recently, Sensabaugh et al, in European patent application No. 174,645, described smoking articles having fuel elements, preferably carbonaceous fuel elements, normally in a conductive heat exchange relationship with a substrate bearing an aerosol forming material. Such smoking articles are believed to be capable of providing the benefits and advantages associated with conventional cigarette smoking, without delivering considerable quantities of incomplete combustion and pyrolysis products, and without the many drawbacks associated with the previously mentioned smoking articles. However, in the embodiments described by Sensabaugh et al, such as FIG. 3 in European Patent Application 174,645, air contacting the fuel element and combustion gases produced from the burning fuel element are normally drawn through the article and delivered to the user.
There does not appear to be known a smoking article capable of providing the benefits and advantages associated with conventional cigarette smoking, without delivering considerable quantities of incomplete combustion and pyrolysis products, such as is proposed in the aforementioned Sensabaugh European Patent Application, but wherein the air employed in aerosol formation is precluded from directly contacting with the fuel element.